The present invention relates to a method and a device for balancing rotors, in particular for electric motors. This method and associated device fall within the application sector relating to the balancing of rotors of small and medium-sized electric motors with rotors having teeth alternating with recesses arranged in the longitudinal direction.
Both the static and dynamic type of method for balancing a rotor essentially consist of two steps: measurement of the imbalance and elimination of this imbalance or actual balancing.
During the first step, the imbalance of the rotor is measured with a suitable known apparatus which provides the operator with the value of the mass which it is necessary to add or remove and the position on the rotor where this addition or removal must be performed.
During the second step, the operator performs the addition or the removal of material necessary for balancing the rotor itself.
With regard to this second overall balancing process step, methods for removing material are known, said methods consisting in milling or boring the external metal laminations forming the rotor.
In the field of the balancing methods which involve the specific addition of material, methods are known, involving the application of a certain quantity of single or dual-component adhesive paste able to harden either by means of drying in air or by means of exposure to ultraviolet rays.
The use of balancing paste has various drawbacks: firstly, because it is a substance which is generally harmful to a person""s health and, as such, suitable caution and protective means must be used by the operator in order to avoid the consequences arising from contact or prolonged exposure to the substance itself. Secondly, the necessity for hardening and hence stabilization of the paste results in the use of special equipment or methods, relatively long times and consequently high costs.
In particular, in the case of a single-component paste, the use of a specific apparatus designed to stabilize the paste by means of exposure to ultraviolet rays is necessary, with obvious additional costs for the purchase and the use of said apparatus in addition to the amount of time lost waiting for complete stabilization of the paste itself.
Also as regards the dual-component paste, the times are increased since, for the purposes of stabilization, it is necessary first to mix the two components and then wait for stabilization by means of air drying.
In addition to these drawbacks, however, there is also both the uncertainty with regard to application of the exact quantity required and positioning; moreover, there is always the risk of the paste becoming detached during the working life of the rotor.
A further method for balancing rotors by means of the addition of material, in particular for electric motors, is known, said method envisaging the engagement of a U-shaped metal plate to one of the rotor teeth.
This method, although being quick and inexpensive, nevertheless has some drawbacks: firstly, the plate must be forced into its position and this involves a specific operation and the use of a suitable tool; secondly, the plate consists of a ferromagnetic material which is placed within the electromagnetic field of the rotor, thereby constituting anxe2x80x94albeit limitedxe2x80x94local discontinuity in the field which risks negatively influencing the performance of the motor itself. The object of the present invention is that of eliminating the abovementioned drawbacks and providing a method and a device for balancing rotors, in particular for electric motors, by means of the addition of material, which may be applied in a rapid, precise, clean, low-cost and versatile manner, without interfering with operation of the motor, namely without affecting the electromagnetic field of the motor itself.
Said objects are fully achieved by the method and device for balancing rotors, in particular for electric motors, according to the present invention, which is characterized by the contents of the claims indicated below.
In particular the method for balancing rotors in question, by means of the addition of material, is characterized by the fact that the actual balancing step consists of the insertion of one or more self-locking balancing devices, made of non-ferromagnetic material, inside one or more recesses formed in the rotor and designed to seat the rotor winding, these devices being of the type having a mass which is known and can be determined beforehand in terms of both its amount and its distribution.
In particular, the abovementioned method is characterized by the fact of being able to perform both static and dynamic type balancing, by suitably choosing between a flat-type and bulb-shaped device.
In addition to the method, the present invention also relates to device for balancing rotors which is characterized in that it may be formed so as to be inserted and self-locking inside a recess formed in the rotor and designed to seat the rotor winding.
In fact, although being able to vary in shape, size and proportions, the device for balancing rotors is characterized by the fact it is made of non-ferromagnetic material and consists of a head, a body extending longitudinally with respect to the axis and a resilient end, for allowing insertion into the recess and locking thereof by small tooth means.